President-elect Donald Trump says Venezuela's embattled opposition leader must be protected as President Nicolas Maduro takes the oath of office for a third six-year term.

Maria Corina Machado was freed shortly after she was detained amid gunshots while leaving a protest in eastern Caracas.

Machado, a former lawmaker who has spearheaded the opposition to President Nicolas Maduro in recent years, was detained by security agents who shot at motorcycles she was using to leave a protest in Caracas, the capital, according to posts on social media from her party. She was freed about an hour later, according to the party.